Update Chapter 5

Author: ShiqiYu

week05/Lecture05.pptx

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+#include <stdio.h>
+#include <stdlib.h>
+
+void foo()
+{
+    int* p = (int *) malloc( sizeof(int));
+    return;
+} //memory leak
+
+int main()
+{
+    int * p = NULL;
+    
+    p = (int *) malloc(4 * sizeof(int));
+    // some statements
+    p = (int *) malloc(8 * sizeof(int));
+    // some statements
+    free (p);
+    // the first memory will not be freed
+
+    for(int i = 0; i < 1024; i++)
+    {
+        p = (int *) malloc(1024 * 1024 * 1024);
+    }
+    printf("End\n");
+
+    return 0;
+}

week05/examples/memoryleak.c

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+#include <iostream>
+using namespace std;
+
+struct Student{
+    char name[4];
+    int born;
+    bool male; 
+};
+
+int main()
+{
+    //allocate an int, default initializer (do nothing)
+    int * p1 = new int; 
+    //allocate an int, initialized to 0
+    int * p2 =  new int();
+    //allocate an int, initialized to 5
+    int * p3 =  new int(5); 
+    //allocate an int, initialized to 0
+    int * p4 =  new int{};//C++11    
+    //allocate an int, initialized to 5
+    int * p5 =  new int {5};//C++11
+
+    //allocate a Student object, default initializer
+    Student * ps1 = new Student;
+    //allocate a Student object, initialize the members
+    Student * ps2 = new Student {"Yu", 2020, 1}; //C++11
+
+    //allocate 16 int, default initializer (do nothing) 
+    int * pa1 = new int[16];
+    //allocate 16 int, zero initialized 
+    int * pa2 = new int[16]();
+    //allocate 16 int, zero initialized 
+    int * pa3 = new int[16]{}; //C++11
+    //allocate 16 int, the first 3 element are initialized to 1,2,3, the rest 0
+    int * pa4 = new int[16]{1,2,3}; //C++11
+
+    //allocate memory for 16 Student objects, default initializer
+    Student * psa1 = new Student[16];
+    //allocate memory for 16 Student objects, the first two are explicitly initialized
+    Student * psa2 = new Student[16]{{"Li", 2000,1}, {"Yu", 2001,1}}; //C++11
+    cout << psa2[1].name << endl;
+    cout << psa2[1].born << endl;
+
+    //deallocate memory
+    delete p1;
+    //deallocate memory
+    delete ps1;
+
+    //deallocate the memory of the array
+    delete pa1;
+    //deallocate the memory of the array
+    delete []pa2;
+
+    //deallocate the memory of the array, and call the destructor of the first element
+    delete psa1;
+    //deallocate the memory of the array, and call the destructors of all the elements
+    delete []psa2;
+
+    return 0;
+}

week05/examples/newdelete.cpp

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+#include <iostream>
+using namespace std;
+
+int main()
+{
+    int a = 0;
+    int b = 0;
+    int c = 0;
+    
+    cout << &a << endl;
+    cout << &b << endl;
+    cout << &c << endl;
+
+    int * p1 = (int*) malloc (4);
+    int * p2 = (int*) malloc (4);
+    int * p3 = (int*) malloc (4);
+
+    cout << p1 << endl;
+    cout << p2 << endl;
+    cout << p3 << endl;
+
+    free(p1);
+    free(p2);
+    free(p3);
+
+    return 0;
+}